android title won't show in toolbar

Question

I have an xml that I use with so many activities with fragments file but my problem is that I can\'t display the text I want in the toolbar, I use that xml that way because

Answer 1

I actually had to get the toolbar_title to set the text into each different activity:

    toolbar = findViewById(R.id.toolbar);
    toolbarTitle = findViewById(R.id.toolbar_title);   //<----- here
    toolbarTitle.setText(getString(R.string.my_activity_toolbar_title));
    setSupportActionBar(toolbar);
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);